Interactive effects of increased temperature, elevated pCO(2) and different nitrogen sources on the coccolithophore Gephyrocapsaoceanica

As a widespread phytoplankton species, the coccolithophore Gephyrocapsaoceanica has a significant impact on the global biogeochemical cycle through calcium carbonate precipitation and photosynthesis. As global change continues, marine phytoplankton will experience alterations in multiple parameters, including temperature, pH, CO(2), and nitrogen sources, and the interactive effects of these variables should be examined to understand how marine organisms will respond to global change. Here, we show that the specific growth rate of G. oceanica is reduced by elevated CO(2) (1000 μatm) in [Image: see text] -grown cells, while it is increased by high CO(2) in [Image: see text] -grown ones. This difference was related to intracellular metabolic regulation, with decreased cellular particulate organic carbon and particulate organic nitrogen (PON) content in the [Image: see text] and high CO(2) condition compared to the low CO(2) condition. In contrast, no significant difference was found between the high and low CO(2) levels in [Image: see text] cultures (p > 0.05). The temperature increase from 20°C to 25°C increased the PON production rate, and the enhancement was more prominent in [Image: see text] cultures. Enhanced or inhibited particulate inorganic carbon production rate in cells supplied with [Image: see text] relative to [Image: see text] was observed, depending on the temperature and CO(2) condition. These results suggest that a greater disruption of the organic carbon pump can be expected in response to the combined effects of increased [Image: see text] /[Image: see text] ratio, temperature, and CO(2) level in the oceans of the future. Additional experiments conducted under nutrient limitation conditions are needed before we can extrapolate our findings to the global oceans.